https://leetcode.com/problems/longest-palindromic-substring/
public String longestPalindromeExpandAroundCenter(String s) {
if (s == null || s.length() < 1) return "";
int start = 0, end = 0;
for (int i = 0; i < s.length(); i++) {
int len1 = expandAroundCenter(s, i, i);
int len2 = expandAroundCenter(s, i, i + 1);
int len = Math.max(len1, len2);
if (len > end - start) {
start = i - (len - 1) / 2;
end = i + len / 2;
}
}
return s.substring(start, end + 1);
}
private int expandAroundCenter(String s, int left, int right) {
int L = left, R = right;
while (L >= 0 && R < s.length() && s.charAt(L) == s.charAt(R)) {
L--;
R++;
}
return R - L - 1;
}
System.out.println(new LongestPalinSubstring().longestPalindromeExpandAroundCenter("cbbd"));
Print: bb
And the code will be accepted. But when I convert Java code to JavaScript code, it failed.
var longestPalindrome = function (s) {
if (s == null || s.length < 1) return "";
var start = 0, end = 0;
for (var i = 0; i < s.length; i++) {
var len1 = expandAroundCenter(s, i, i);
var len2 = expandAroundCenter(s, i, i + 1);
var len = Math.max(len1, len2);
if (len > end - start) {
start = i - (len - 1) / 2;
end = i + len / 2;
}
}
return s.substring(start, end + 1);
};
var expandAroundCenter = function (s, left, right) {
var L = left, R = right;
while (L >= 0 && R < s.length && s[L] == s[R]) {
L--;
R++;
}
return R - L - 1;
}
console.log(longestPalindrome("cbbd"))
cbb
Why JS code return "cbb" instead of "bb"?
This has to do with the differences between Java's integer division and Javascript's floating-point version.
Replacing this:
if (len > end - start) {
start = i - (len - 1) / 2;
end = i + len / 2;
}
with this:
if (len > end - start) {
start = i - Math.floor((len - 1) / 2);
end = i + Math.floor(len / 2);
}
should fix it.
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